If you don't need the proprietary driver (afaik the open source driver is more stable but lacks 3D acceleration), you should remove them and use the open driver. If you need them (eg. for games) I can't help you because I'm using Nvidia.But I think I've seen somewhere on the forum how to use them.

@ amandus: 1st: Did you read the notice? 2nd: Did you use kernel switcher to install the 3.6 kernel?

@ creh :The opensource ATI drivers have both 2d (KMS + X11) and 3d acceleration (mesa + gallium), just not as fast or as many features as the proprietary one, however that's changing very quickly as the gallium drivers mature.